1. Field of the Invention
The present invention relates to a rotor for a dynamo-electric machine provided with magnetic components arranged between adjacent claw-shaped magnetic poles to reduce magnetic flux leakage between the claw-shaped magnetic poles.
2. Description of the Related Art
FIG. 13 is a cross section of a conventional vehicle alternator which is an example of a dynamo-electric machine to which the present invention can be applied, FIG. 14 is a perspective view of the rotor in FIG. 13, and this alternator is provided with: a case 3 comprising an aluminum front bracket 1 and an aluminum rear bracket 2; a shaft 6 to which a pulley 4 is secured, disposed in the case 3; a roundel-shaped rotor 7 secured to the shaft 6; fans 5 secured to both sides of the rotor 7; a stator 8 secured to the inner wall of the case 3; slip rings 9 which supply electric current to the rotor 7, secured to the other end of the shaft 6; a pair of brushes 10 which move in contact with the slip rings 9; brush holders 11 which accommodate the brushes 10; a commutator 12 in electrical contact with the stator 8 which converts an alternating current generated in the stator 8 to a direct current; a heat sink 17 fitted into the brush holder 11; and a regulator 18 secured in contact with the heat sink 17 to regulate the magnitude of the alternating voltage generated in the stator 8.
The rotor 7 is provided with: a rotor coil 13 which generates magnetic flux when an electric current is passed through it; and a pole core 14 in which magnetic poles are formed by the magnetic flux generated by the rotor coil 13, disposed so as to cover the rotor coil 13. The pole core 14 comprises a first pole core body 21 and a second pole core body 22 which are mutually intermeshed. The first pole core body 21 and the second pole core body 22 are made of iron, and have claw-shaped magnetic poles 23, 24 respectively. Magnets 19 of trapezoidal cross-section, which are polarized so as to reduce magnetic flux leakage between the claw-shaped magnetic poles 23, 24, are secured by adhesive to adjacent claw-shaped magnetic poles 23, 24.
The stator 8 is provided with: a stator core 15; and a stator coil 16, which is a conductor wound around the stator core 15 which generates an electric current in response to changes in the magnetic flux generated by the rotor coil 13 resulting from the rotation of the rotor 7.
In a vehicle alternator of the above construction, a current is supplied by a battery (not shown) through the brushes 10 and slip rings 9 to the rotor coil 13, and a magnetic flux is generated, whereby the claw-shaped magnetic poles 23 of the first pole core body 21 are polarized with a north-seeking (N) pole, and the claw-shaped magnetic poles 24 of the second pole core body 22 are polarized with a south-seeking (S) pole. At the same time, the pulley 4 is driven by the engine and the rotor 7 is rotated by the shaft 6, so that a rotating magnetic field is imparted to the stator coil 16 and electromotive force is generated in the stator coil 16. This alternating electromotive force is converted to a direct current by means of the commutator 12 and its magnitude is regulated by the regulator 18, and the battery is recharged.
The rotor 7 of the conventional vehicle alternator, in which magnets 19 are secured by adhesive to the claw-shaped magnetic poles 23, 24, suffers from the following problems:
a) As the rotor 7 rotates, each of the magnets 19 is subjected to a large centrifugal force, and each is supported against this centrifugal force by tapered surfaces 23a, 24a on the claw-shaped magnetic poles 23, 24, as shown in FIG. 15, but the magnets 19 are not subjected to a uniform load, and so the magnets 19 are easily damaged. The reason that the magnets 19 are not subjected to a uniform load is that the magnets 19 are not arranged parallel to the axis Z of the rotor 7. The distance (r.sub.1, r.sub.2) from the axis Z is different for each part of the magnet 19, as shown in FIG. 16, and so the centrifugal force is different; and PA1 b) The magnets 19 are secured by means of adhesive in close contact between the claw-shaped magnetic poles 23 and claw-shaped magnetic poles 24 and a corresponding degree of milling precision is required for the claw-shaped magnetic poles 23, 24, and for that reason cutting work is required after forging the claw-shaped magnetic poles 23, 24 from raw materials, which makes the manufacturing process complicated and raises production costs. Also, because there is no space between the claw-shaped magnetic poles 23, 24 and the magnets 19, there is a risk that the delicate magnets 19 may be damaged when they are inserted between the claw-shaped magnetic poles 23 and claw-shaped magnetic poles 24. PA1 wherein the magnetic body is provided with prismatic mediating portions each comprising: a magnetic component polarized so as to reduce magnetic flux leakage between the claw-shaped magnetic poles; and a cover portion made of resin which covers the magnetic component, PA1 and wherein spaces are formed between the mediating portions and the claw-shaped magnetic poles.